3.2 Summary Questions & Exam Style Questions

Question 1

Explain how hydrogen bonds form. [3]

Answer 1

Oxygen and hydrogen share electrons unequally when they bond. Oxygen, has a greater share/ is
more negative (1). Hydrogen, has a smaller share/is more positive (1). The more negative oxygen
atom is attracted to the more positive hydrogen atom (1).

Question 2

Explain why water is a polar molecule. [2]

Answer 2

Water is composed of hydrogen and oxygen atoms and bonds between oxygen and hydrogen
involve unequal sharing of electrons (1) in bonds resulting in the oxygen atom being more negative
and the hydrogen atoms being more positive (1).

Question 3

Suggest, with reasons, which properties of water make it such an important component of blood. [5]

Answer 3

Liquid so transport medium (1); polar solvent (1); (many) biological molecules / examples
(e.g., enzymes, glucose), are polar (1); ions are charged (1); coolant so (relatively) resistant to
temperature change (1).

Question 4

Water forms the basis of the stroma in chloroplasts and the matrix in mitochondria.

Describe which properties of water make it such an important component of these particular organelles. [5]

Answer 4

(water is) liquid (1) / allows movement of substrates and enzymes (1) / idea that this is necessary
for reactions to occur (1) / (water is) a polar solvent (1) / substrates / enzymes / products, are, polar /
ionic (1) / (water is) substrate for (some) reactions (1).